Earth working tools are commonly used for a number of tasks, including trenching, scraping, boring, post hole digging, and so on. The tools often form part of a self-propelled vehicle which also supplies power to the earth working tool. The number and variety of tasks to be performed by the earth working tool demand versatility in positioning the tool with respect to the grade or level of the ground. The vehicle is ordinarily limited to a fixed position with respect to the supporting ground surface. Accordingly, it is necessary to selectively adjust the position of an upright working tool with respect to the portable vehicle upon which it is mounted in order to perform the task for which the tool is to be used.
In driving fence posts or in digging post holes it is desirable that the post be driven or the hole be dug in a vertical direction. A post driver, for example, rigidly mounted on a tractor would be incapable of driving vertical posts.
An apparatus for manually adjusting the position of a post driving device with respect to the ground surface is disclosed in U.S. Pat. No. 2,940,267. A device having three hydraulic cylinders for adjusting the angle of an upright earth boring apparatus, and disclosed in U.S. Pat. No. 3,576,218, is capable of only a limited lateral adjustment of the tool and utilizes a pair of the cylinders for longitudinal tool adjustment. This difficulty is solved by the present invention which provides for an upright post driver being selectively oriented with respect to the tractor in any direction to vertically drive posts in uneven terrain.